1. Technical Field
The present invention relates to a measuring method of scintillation appearing on a display image of a display device installed with a light source and to a scintillation measuring device.
2. Related Art
There have been widely used various types of display devices for displaying an optical image which is formed by modulating a source light in accordance with image information, the display devices being typically a CRT (Cathode Ray Tube), a liquid crystal display, a plasma display, an organic EL (electroluminescence) display, a projector and the like.
A person observing a display image on a display panel of a display device or a display image projected onto a screen sometimes senses a whitish bright scintillation in a part of the display image when the person slightly moves ones line of sight. The scintillation is considered to be caused by light-diffusion, reflection or the like generated by a light-diffusing member, a lens, etc. provided to the display panel. The scintillation is sensed when a pixel having a luminance higher than other parts exists in the display image. Since the scintillation is very minute and is not always sensed depending on a position for observing the display image, it is difficult to detect the scintillation simply by capturing and processing the display image.
With such background, a technology for measuring the scintillation has not been known.
Incidentally, in other fields, there has been known a technology for measuring a gloss of a painting surface of an automobile body (Document 1: JP-A-7-27704). Herein, by illuminating the painting surface using a light source device including a slit plate having a lot of slits arranged in parallel and a diffuser plate, an image of a parallel grid pattern is formed on the painting surface and the painting surface is captured. Then, a changing amount of a signal level changing in a direction orthogonal to the parallel grid pattern on the painting surface in the captured image is detected by an image processing device. Based on an inclination angle obtained by the changing amount of the signal level, the gloss of the paining surface is measured.
There has also been known a technology for measuring a surface quality of a painting surface, in which the painting surface is illuminated by an LED (Light Emitting Diode) light source and a reflection image reflected by the illumination are captured using a camera. Then, image processing is performed to measure gloss, sharpness and orange-peel of the painting surface based on: difference in luminance among pixels caused by difference of diffusion levels in the reflection image of the painting surface; variation in reflectivity at edges; and the like (Document 2: “Paint Quality measurement”, [online], Perceptron Asia Pacific Ltd [retrieved on Aug. 17, 2005], Internet <URL: http://www.perceptron.co.jp/product/paint/autospect.html>).
There has been known another technology for measuring a surface quality of a painting surface, in which the painting surface is illuminated at a plurality of angles, and images of the painting surface are captured for each of the illumination angles. Metallic, matt and orange-peel characteristics of the painting surface are measured based on difference in color between the captured images (Document 3: “Multi-Angle Image Colorimeter” [online], KURABO INDUSTRIES LTD., [retrieved on Aug. 17, 2005], Internet <URL: http://www.kurabo.cojp/el/af/afhl—01.html>).
Although there are technologies capable of measuring a surface quality of a painting surface as disclosed in Document 1 to 3, all of the technologies employ external light sources and cannot be applied to a measurement principle for measuring quality of a display image of a display device incorporating a light source (including a light emitter).
In recent information society, various display devices have been increasingly used for watching television programs, browsing the Internet, watching video software, while being used in presentations, conferences and exhibitions, which makes the display devices more and more important. Accordingly, further improvement of image quality of the display devices is demanded. It is required that a number of display devices with high image quality be provided in offices, cities, schools, homes, etc. with consistent quality.
In order to realize such demand, a predetermined scintillation quality needs to be ensured by performing an inspection for quantitatively measuring scintillation of display images in manufacturing the display devices.
In addition, it is desired to develop a display device free from generation of scintillation by utilizing quantitatively-measured scintillation levels.